1. Field of the Invention
The present invention relates to methods of manufacturing diffusion bonded products, e.g. engine valves. The present invention also relates to products manufactured by such methods.
2. Description of the Related Art
Japanese Laid-Open Patent Publication No. 2-89535 teaches a method of manufacturing a titanium based engine valve by using a diffusion bonding technique. In the method of this publication, a valve head and a valve shaft are diffusion bonded to each other by treating these parts with heat within a vacuum furnace, while the valve head and the valve shaft are pressed against each other by a predetermined pressure by means of a hot press machine that is disposed within the vacuum furnace.
According to the method of this publication, in order to press a valve head and a valve shaft against each other within a vacuum furnace, a large-scaled hot press machine must be accommodated within the vacuum furnace. Therefore, the efficiency of the process for diffusion bonding was relatively low, so that the manufacturing costs have been increased.